In a radio communication system, to schedule radio resources effectively and efficiently, the network device needs to obtain enough downlink channel state information that has certain accuracy. To make the network device obtain the downlink channel state information, the mobile station needs to measure and report such information.
The method for the mobile station to measure and report includes the following. The network device sends a certain reference signal for measuring the downlink channel to the mobile station in the coverage area; after receiving the reference signal, the mobile station obtains a downlink channel response through measurement and calculation, and obtains the channel state information according to the downlink channel response. Afterward, the mobile station properly quantizes the downlink channel state information according to a certain rule, and feeds back the downlink channel state information to the corresponding network device.
The CoMP (Coordinated multipoint processing, coordinated multipoint processing) multi-cell downlink channel estimation technology is introduced to achieve higher user throughput. In a CoMP scenario, multiple cells provide data transmission services for a same UE (User Equipment, user equipment) simultaneously. What is different from a traditional single-cell service is that, in a CoMP scenario, the UE needs to measure reference signals delivered by multiple serving base stations simultaneously, and estimate the downlink channel information from multiple base stations and feed back the information.
A method for measuring channel state information in the prior art is: The network device delivers a CRS (common reference signal, common reference signal) to the UE, and the UE estimates the downlink channel according to the CRS. The CRS may be used for data coherence demodulation and channel measurement at the same time. Taking the radio transmission system shown in FIG. 1 as an example, this system includes cells (cell) 1, 2 and 3 and UE1. Cell 1 is a serving cell of the UE, and cells 1, 2, and 3 make up a CoMP measurement set of UE1. By detecting all downlink CRSs from each cell, UE1 obtains the downlink channel state information of each cell. UE1 measures the RE (Resource element, resource element) occupied by all CRSs at each subframe to obtain the downlink channel state information of each cell. Afterward, UE1 feeds back the obtained downlink channel information of each cell to each cell respectively.
In practical applications, the CRS may be replaced with CSI-RS (CSI-RS Channel State Information Reference signal, channel state information reference signal). The period of the CRS is different from the period of the CSI-RS, and the density of the occupied REs also varies between the CRS and the CSI-RS. The density of the RE refers to the number of REs on each RB (resource block, resource block) of each subframe from which the reference signals CRS and CSI-RS are sent, namely, number of REs occupied by the reference signals on each RB of the subframe.
In the process of implementing the present invention, the inventor finds at least the following problems in the prior art: When the UE performs channel measurement for each cell, the UE measures the REs occupied by all reference signals on each subframe, which leads to great workload of the UE in the channel measurement.